The present invention relates to saws for cutting concrete and, more particularly, to saws for cutting grooves in green concrete to prevent random cracking.
Concrete slabs are prone to cracking as a result of expansion and contraction as they cure, and as a result of exposure to environmental temperature changes. Uncontrolled, such cracks can form anywhere within the concrete slab.
One method of controlling the formation and location of cracks in the slab is to provide a relatively shallow groove along the surface of the concrete. Since the slab is weakest along the cross sectional plane defined by such a groove, potential cracks are more likely to form within the plane defined by the groove than in the area containing no formed or saw cut groove. Providing regularly spaced grooves along the surface of a large concrete slab has become a widely accepted method of controlling the cracks and localizing the cracks within the groove where they will be less visible and aesthetically positioned.
Several methods and devices are known for creating grooves in the surface of newly poured concrete. One method is to form the grooves with a hand held tool, such as a trowel, while the concrete is still soft enough to be worked by hand. Another method uses a saw to cut a groove into the concrete while the concrete is green, i.e., still relatively soft, but hard enough to support such a device.
One such type of cutting device is disclosed U.S. Pat. No. 5,056,499. This patent discloses a concrete cutting device having a slotted skid plate through which a circular saw blade projects for cutting the concrete. The saw blade is mounted on a frame that is supported on the concrete surface by the skid plate and several wheels. The skid plate contacts the concrete adjacent the area being cut by the blade to prevent undesirable ravelling and chipping of the surface and maintain the integrity of the concrete surface near the cut. To cut the groove, the device is pushed across the surface of the concrete as the saw blade rotates. Because the device is supported by a skid plate in direct contact with the concrete surface, the device actually skids along the surface as it moves.
Concrete saws of the type described above have several disadvantages. Desirably, green concrete should be cut as early as possible without marring its surface. While devices of the type previously discussed are light in weight, sliding the skid plate across the surface of the concrete tends to mar the finish. Additionally, skidding, as opposed to rolling, requires additional force to propel the unit across the surface, increasing the tendency for the operator to push the cutting device down into the concrete, further marring the surface. Furthermore, the combination of a skid plate on one side of the cutting device and wheels on the other side can cause the saw device to yaw relative to the direction of travel. Such yawing skews the blade relative to the direction of travel resulting in a wider, more unsightly groove in the concrete and chipping and ravelling.
One previously proposed solution to this problem is a green concrete cutting saw that is mounted on a wheeled support, in which anti-spalling rollers are positioned generally adjacent to the blade exit point. However, the rollers were located at a set radial distance from the blade shaft on the blade guard. Depending upon the depth of cut, the rollers would not be aligned with the blade exit point from the surface of the green concrete being cut. This resulted in some chipping or spalling of the green concrete along the edge of the cut.
It would be desirable to provide a saw for cutting green concrete which eliminates this problem by maintaining the position of the anti-spalling rollers generally aligned with the blade exit point from the surface of the green concrete being cut throughout the operative cutting range of the saw.
It would also be desirable to prevent chipping and maintain the surface integrity of the concrete adjacent the groove as the cut is made.
Briefly stated, the present invention provides an apparatus for cutting green concrete. The apparatus includes a frame having a plurality of support wheels located thereon. A prime mover assembly is connected to the frame, and a concrete cutting blade is drivingly connected to the prime mover, preferably through the use of a traction means such as a chain or belt. The blade is mounted for generally upward and downward movement relative to the frame for engaging and disengaging from a surface to be cut. A carriage having an anti-spalling roller mounted thereon is connected to the frame. The carriage position is simultaneously adjusted with the upward and downward movement of the blade such that a surface contact portion of the anti-spalling roller is maintained in alignment with a blade exit location for an operative range of cutting depths.